The Financial Services Authority deserves to be censured for making UK financial regulation look ridiculous. The £30m fine dished out to the Prudential is wildly over the top when you remember that UBS copped only a similar sum for failing to detect Kweku Adeboli's fraudulent trading.

Which offence is more serious? Failing to give the regulator a heads-up on a possible deal, even a big one, or allowing a trader to run riot and clock up a £1.2bn loss? Come on, UBS's sins were many times greater.

And the censure for chief executive Tidjane Thiam is beyond parody. Think about what has been going on in our big banks in recent years. Libor has been rigged. US sanctions against Iran have been breached. Rules against money laundering have been flouted. Small businesses have been fleeced via interest rate swaps. Punters have been stuffed with inappropriate and overpriced PPI policies. Yet no chief executive of a big bank has been censured for anything. Thiam, by contrast, has been put in the stocks – he is the only FTSE 100 chief executive to receive a censure from the FSA.

At a push, one might agree that the Pru kept quiet for too long. The $35bn (£23.2bn) purchase of AIA would have been a very big transaction. It would have involved a £14.5bn rights issue and, conceivably, there were implications for UK financial stability. Yet the FSA's rule on disclosure is vague – principle 11 imposes an obligation to "disclose appropriately information of which the FSA would reasonably expect notice".

That phrasing introduces an element of judgment. The detail that seems to have annoyed the FSA was Thiam's failure to mention the Pru's ambition to buy AIA at a regular supervisory meeting on 12 February; a non-binding proposal had been dispatched to AIG, AIA's owner, by that stage. But Thiam's reticence at the meeting is easy to understand. Loose talk costs deals and a leak could have been a killer.

Yes, on balance, Thiam waited too long to tell the FSA – and, indeed, it was a newspaper report of the talks that came first. But a modest fine for the Pru plus criticism of the entire board, not just the chief executive, would surely have made the FSA's point about the importance of prompt disclosure. Better still, the regulator could have offered clearer guidance on when firms are supposed to report possible deals.

The big fine and censure make it look as if the FSA, in its final hours, is trying to make up for lost time. It is a classic case of UK regulation at its worst: miss the big stuff and then stamp on minor infringements.